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Cotonou, Benin

Rodenburg J.,Africa Rice Center | Saito K.,AfricaRice | Irakiza R.,Africa Rice Center | Makokha D.W.,Africa Rice Center | And 2 more authors.
Weed Technology | Year: 2015

Time requirements, weed control efficacy, and yield effects of three labor-saving weed technologies were tested against hand weeding during three seasons in 2012 and 2013. The technologies included two hand-operated mechanical weeders, the straight-spike and the twisted-spike floating weeder, and the PRE application of oxadiazon. The straight-spike floating weeder reduced weeding time by 32 to 49%, the twisted-spike floating weeder reduced weeding time by 32 to 56%, and the application of herbicide required 88 to 97% less time than hand weeding. Herbicide application provided the best weed control in two of the three seasons. No differences in weed control efficacy were observed between mechanical and hand weeding. Yield differences were only observed in season 3 with higher rice yields after PRE application of oxadiazon compared with other weed management treatments. Nomenclature: Oxadiazon; rice, Oryza sativa L. Source

Diwani T.N.,German Development Service D.E.D | Asch F.,University of Hohenheim | Becker M.,University of Bonn | Mussgnug F.,AfricaRice
Journal of Plant Nutrition and Soil Science | Year: 2013

Kakamega district in Western Kenya represents the smallholder farming systems typical for much of the densely populated humid highlands in East Africa. A specific feature, however, is the presence of a protected forest reserve (Kakamega Forest National Park), covering some 20% of the district area. Year-round crop production with little use of external inputs is resulting in declining soil fertility and crop yields. Technologies to counteract fertility constraints are rarely implemented, as they do not consider system diversity or farm-specific characteristics. We surmised that farm type-specific targeting of technology options to address soil fertility-related production constraints would reduce the anthropogenic pressure on the resources of the adjacent Kakamega rainforest reserve. Based on Kenyan national census data, we selected 168 farms in physical proximity of the Kakamega forest and characterized them regarding production system and soil attributes. Cluster and principal component analyses identified five distinct farm categories. Three representative farms from each cluster group were subsequently selected to establish labor-use patterns, draw resource-flow maps, and determine NPK balances. Small subsistence-oriented farms were most common (> 50%), with maize yields of 0.9 t ha-1 (Cluster 1). Most farmers relied on the forest to provide fire wood, animal feed, and medicinal plants. Mixed farms, combining subsistence maize with industrial crops, were differentiated by soil type, with tea being grown on Ferralsol (Cluster 3), and sugar cane being grown on Acrisol (cluster 4). The dependence on forest resources was limited to animal grazing and the collection of feed stuff (Cluster 3), or the extraction of medicinal plants (Cluster 4). Only few farms showed a high degree of market orientation of the food-crop production. These comprised either small farms with high investments in fertilizer and maize yields close to 2 t ha-1 (Cluster 2), or larger farms (1.6-3.9 ha) with low fertilizer but high hired-labor use (Cluster 5). Their reliance on forest resources was generally low. Resource flows showed mainly patterns of nutrient export in subsistence farms, and more complex flow patterns, involving several farm compartments, in the diversified farms. Partial nutrient balances were strongly negative for N and K, irrespective of soil or farm type. Soil-fertility characteristics reflected the nutrient balances with generally low C and N in all farms on Acrisol, and low P in farms not applying mineral fertilizers or farmyard manure. The proposed typology is expected to improve the targeting of technologies addressing soil fertility-related production constraints, and to reduce the pressure on forest resources. This is of particular importance in the case of small-scale subsistence and mixed farms close to the forest margin. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Seguni Z.S.K.,Mikocheni Agricultural Research Institute | Way M.J.,Imperial College London | Van Mele P.,AfricaRice
Crop Protection | Year: 2011

In tropical Africa and Asia, two species of the predatory ant genus, Oecophylla, play a crucial role in protecting tree crops against pests and enhancing the quality of fruits and nuts. As predatory effectiveness is influenced by the presence of other dominant ant species, understanding the ecological factors at work in agroecosystems lies at the basis of conservation biological control. Over three and a half years, the effect of ground vegetation management on the beneficial tree-nesting ant Oecophylla longinoda (Latreille) and its competitor, the ground-nesting ant, Pheidole megacephala (Fabricius), was studied in a citrus orchard in Tanzania. When ground vegetation was present, P. megacephala tolerated O. longinoda and to some extent cohabited with this ant in citrus trees. However, after clean cultivation, P. megacephala displaced O. longinoda from tree crowns and became the sole occupant of the majority of trees. Displacement could be reversed by reversing the weed management regime, but this took time. Two years after the establishment of ground vegetation about half of the trees were colonized by Oecophylla only. Maintaining ground vegetation in tree crop plantations benefits the establishment and abundance of Oecophylla over Pheidole and is recommended in order to improve the efficiency of biological control of tree pests. The use of Amdro ant bait (hydramethylnon) to control P. megacephala is discussed. Boosting agroecological innovations, such as the one described in this paper, could benefit smallholder producers. © 2011 Elsevier Ltd. Source

Yamano T.,International Rice Research Institute | Arouna A.,AfricaRice | Labarta R.A.,International Center for Tropical Agriculture | Huelgas Z.M.,International Rice Research Institute | Mohanty S.,International Rice Research Institute
Global Food Security | Year: 2016

To meet rising demand for rice, it is estimated that the global rice production needs to increase by 116 million tons by 2035. Much of the increase has to come from smallholder rice farmers in developing countries. In this article, we review 25 evaluation studies on new rice technologies and practices that have been tried and used by smallholder rice farmers in developing countries. Stress-tolerant rice varieties are found among promising new rice varieties. African farmers benefit from New Rice for Africa (NERICA) varieties. Some natural resource management (NRM) practices have been evaluated in farmer trials and found beneficial. However, the NRM evaluation studies faced with difficulties in defining NRM "technology" and "adoption", and the difficulties remain as future challenges for evaluation studies. © 2016. Source

Djedatin G.,AfricaRice | Djedatin G.,University Abomey Calavi | Ndjiondjop M.-N.,AfricaRice | Mathieu T.,CNRS Plant Genome and Development Laboratory | And 6 more authors.
Plant Disease | Year: 2011

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial blight in rice, one of the most devastating diseases of rice worldwide. African X. oryzae pv. oryzae strains belong to a clear genetic group distinct from those of Asia. Three new races of the pathogen were characterized among strains from West Africa. We evaluated 107 Oryza glaberrima accessions for resistance to bacterial blight under greenhouse conditions. Six-week-old seedlings were inoculated with five different African X. oryzae pv. oryzae strains originating from the West African nations of Burkina and Mali and representing different races (A1, A2, and A3). Philippine X. oryzae pv. oryzae strain PXO86 (race 2) was also used. Most (48%) of the accessions of O. glaberrima were highly susceptible to X. oryzae pv. oryzae strains from Burkina, while 20 and 36 were resistant to X. oryzae pv. oryzae strains from Mali and the Philippines, respectively. CAPS markers and dot blot assays were used for detection of resistance genes xa5 and Xa21 from a selected set of O. glaberrima accessions. Our results suggest that the O. glaberrima germplasm contains a narrow genetic base for resistance to X. oryzae pv. oryzae. Sources of resistance identified among O. glaberrima are recommended for rice breeding programs to develop bacterial blightresistant cultivars for West Africa. © 2011 The American Phytopathological Society. Source

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